The first Europeans to land in America traveled west to do so. Their descendants continued moving west for the next 250 years. They were joined by other Europeans in this migration, as well as African-Americans and Native Americans—some moved forcibly. In time their westward movement brought them into contact with Pacific Islanders and Asians, some of them immigrants to the expanding United States. The documents in this collection present the reasons Americans gave for and against westward expansion and their thoughts on the political, moral, and economic issues it raised. Preeminent among these issues were slavery and the fate of the Native Americans. Americans were also concerned about where and when westward expansion should end and the effect that its ending would have on the nation. The documents and images in this volume also present the experiences of settlers, explorers, farmers, former slaves, and Indians struggling to build new lives in the west or hold on to aspects of their old lives as westward expansion transformed the land, those who lived on it, and the United States itself. To understand this story, it is wise to avoid presentism—applying today’s standards and sentiments to the past—even while rightly maintaining our moral objections to blatant racial prejudice and injustice. We must take into account the facts as they were as well as the perspectives of politicians, businessmen, and ordinary citizens. Three facts stand out. First, there was the search of the European settlers and their descendants for a better, freer life, coupled with a massive demographic wave, fed by immigration. The American Revolution and the Constitution were designed to enable that better life under a novel form of government—a federal democratic republic. There were no barriers that any government of the time, much less that envisioned by the Founders, could have erected to stem the tide of a restless, enterprising people. The Founders instead intended to manage expansion carefully so that it would be republican in character. They established a template by which territories not yet fully settled, or newly acquired, would follow a distinct path to statehood, at which point they would enter the Union under the Constitution, on par with the other states. Second, there were geopolitical realities which not unreasonably created an imperative for expansion. Some leaders, like Thomas Jefferson, occasionally speculated that westward migration might lead to friendly sister republics on the other side of the Mississippi, but most feared that these would eventually come into conflict with one another, unless united under one federal head. In the worst case, foreign powers would create client states or occupy the western territories themselves, bringing the United States into the maelstrom of European monarchical balance of power rivalries and wars. American statesmen believed that unless the United States became a transcontinental power with no strategic rivals, its republican form of government could not survive. Territorial expansion would be peaceful, orderly, gradual and limited to North America, allowing the United States to expand its commerce overseas. Third, this ideal model of expansion was complicated—to say the least—by a two-fold clash of cultures, or civilizations. The American lands were already occupied by peoples with very different views of what was meant by a better, freer life. Romantic views of the frontier aside, life for the settlers was often very hard. Farmland, individually owned, provided their primary means of existence and hope of a better future. The Indian nations, or tribes, largely held a communal view of land, and claimed extensive holdings. As migration increased, native Americans became far fewer in number than the settlers, and it is only recently that we have realized fully the degree to which diseases carried over from Europe greatly weakened the tribes. The migratory swarm of Americans seeking land, many of them honest and law-abiding, some not, was bound to cause tension and conflict. During negotiations, who could speak authoritatively for the tribes was often in dispute, creating opportunities for misunderstandings and often fraud. As the documents reveal, the U.S. government and private organizations generally tried to do the right thing, by their own lights and the Anglo-American concept of justice. But facts on the ground never allowed full and satisfactory resolution of the civilizational differences. The other clash was within the Union itself, between the increasingly democratic capitalistic north and the oligarchic system of slavery of the south—with the future of the west, and western expansion, very much at stake. The north gradually eclipsed the south in terms of population and wealth, especially as the old northwest entered the Union and anti-slavery sentiment grew (if not a desire for racial equality). The south demanded compensation, in terms of favorable laws, and territorial arrangements and acquisitions that assured a sectional balance. Some politicians, such as James Polk (1795-1849), thought that expansion would ameliorate these sectional tensions by creating a higher national purpose that would unite north and south. The war with Mexico proved exactly the opposite, as did proposals to expand or condone slavery to the southward. Had the southern Confederacy succeeded in the Civil War, the two Americas undoubtedly would soon have disputed possession of the unincorporated western territories and California. Both nations would have been inclined to expand further north and south to balance the other. Abraham Lincoln (1809-1865) resisted secession in part to prevent the geopolitical and moral nightmare of a slavocracy in North America, probably aligned with a hostile European power, rivaling the free republic of a diminished United States. The drive for continental expansion ceased in the generation after the Civil War (Mormonism and Jesuitism), except for the purchase of Alaska. But towards the turn of the twentieth century, some Americans argued for the need to establish overseas colonies (The Significance of the Frontier in American History, My Story) while others argued that this would be a violation of the nation’s republican principles. Whereas this volume focuses on expansion that resulted in the admission of new states, a forthcoming volume (American Foreign Policy) will cover in detail the story of America’s relations with foreign powers and its acquisitions that remained territories.